In recent years, the demand for the lower fuel consumption of automobiles has become increasingly severe in connection with the social need for energy saving. In order to respond to such a demand, a further reduction in the rolling resistance of tire has been requested. As the method for reducing the rolling resistance of tire, the optimization of tire structure has been studied; however, it is generally conducted to use, as the rubber composition for tire, a material as low as possible in heat build-up.
In order to obtain such a rubber composition low in heat build-up, a number of technical studies have hitherto been made to develop a modified rubber for the rubber composition which contains silica and carbon black as a filler. There was proposed, for example, a method for producing a polymer, which comprises subjecting a conjugated diolefin or a conjugated diolefin and an aromatic vinyl compound to anionic polymerization in a hydrocarbon solvent, using, as an initiator, at lest one compound selected from the groups consisting of organic alkali metals and organic alkaline earth metals, to obtain a polymer and then reacting the terminal of the polymer with a particular amino group-containing alkoxysilane compound (see, for example, Patent Document 1).
Further, in order to produce a modified polymer which has a high interaction with silica and carbon black and can give improved fracture resistance, abrasion resistance and low heat build-up, there was proposed a method which comprised conducting a primary modification reaction of reacting the active site of a polymer having, in the molecule, an active site of an organic metal, with a hydrocarbyloxysilane compound and then conducting a secondary modification reaction of reacting the resulting polymer with a hydrocarbyloxysilane compound (see, for example, Patent Document 2).
Patent Document 1: WO 03/029299 A
Patent Document 2: WO 03/048216 A